/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.dialectek.blackguard;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.SharedPreferences;

import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.Closeable;

/**
 * Displays an EULA ("End User License Agreement") that the user has to accept before
 * using the application. Your application should call {@link Eula#show(android.app.Activity)}
 * in the onCreate() method of the first activity. If the user accepts the EULA, it will never
 * be shown again. If the user refuses, {@link android.app.Activity#finish()} is invoked
 * on your activity.
 */
class Eula {
   private static final String ASSET_EULA = "EULA";
   private static final String PREFERENCE_EULA_ACCEPTED = "eula.accepted";
   private static final String PREFERENCES_EULA         = "eula";

   /**
    * callback to let the activity know when the user has accepted the EULA.
    */
   static interface OnEulaAgreedTo {
      /**
       * Called when the user has accepted the eula and the dialog closes.
       */
      void onEulaAgreedTo();
   }

   /**
    * Displays the EULA if necessary. This method should be called from the onCreate()
    * method of your main Activity.
    *
    * @param activity The Activity to finish if the user rejects the EULA.
    * @return Whether the user has agreed already.
    */
   static boolean show(final Activity activity)
   {
      final SharedPreferences preferences = activity.getSharedPreferences(PREFERENCES_EULA,
                                                                          Activity.MODE_PRIVATE);

      if (!preferences.getBoolean(PREFERENCE_EULA_ACCEPTED, false))
      {
         final AlertDialog.Builder builder = new AlertDialog.Builder(activity);
         builder.setTitle(R.string.eula_title);
         builder.setCancelable(true);
         builder.setPositiveButton(R.string.eula_accept, new DialogInterface.OnClickListener()
                                   {
                                      public void onClick(DialogInterface dialog, int which)
                                      {
                                         accept(preferences);
                                         if (activity instanceof OnEulaAgreedTo)
                                         {
                                            ((OnEulaAgreedTo)activity).onEulaAgreedTo();
                                         }
                                      }
                                   }
                                   );
         builder.setNegativeButton(R.string.eula_refuse, new DialogInterface.OnClickListener()
                                   {
                                      public void onClick(DialogInterface dialog, int which)
                                      {
                                         refuse(activity);
                                      }
                                   }
                                   );
         builder.setOnCancelListener(new DialogInterface.OnCancelListener()
                                     {
                                        public void onCancel(DialogInterface dialog)
                                        {
                                           refuse(activity);
                                        }
                                     }
                                     );
         builder.setMessage(readEula(activity));
         builder.create().show();
         return(false);
      }
      return(true);
   }


   private static void accept(SharedPreferences preferences)
   {
      preferences.edit().putBoolean(PREFERENCE_EULA_ACCEPTED, true).commit();
   }


   private static void refuse(Activity activity)
   {
      activity.finish();
   }


   private static CharSequence readEula(Activity activity)
   {
      BufferedReader in = null;

      try {
         in = new BufferedReader(new InputStreamReader(activity.getAssets().open(ASSET_EULA)));
         String        line;
         StringBuilder buffer = new StringBuilder();
         while ((line = in.readLine()) != null) { buffer.append(line).append('\n'); }
         return(buffer);
      }
      catch (IOException e) {
         return("");
      }
      finally {
         closeStream(in);
      }
   }


   /**
    * Closes the specified stream.
    *
    * @param stream The stream to close.
    */
   private static void closeStream(Closeable stream)
   {
      if (stream != null)
      {
         try {
            stream.close();
         }
         catch (IOException e) {
            // Ignore
         }
      }
   }
}
